It is desirable to integrate vertical-cavity surface emitting lasers (VCSELs) on semiconductor circuit chips (usually Si CMOS) via flip-chip bonding to reduce packaging costs, increase performance by eliminating parasitic circuit elements such as wire bonds, and allow for the formation of integrated transmitter arrays. It would be particularly useful to integrate 850 nm VCSELs since that wavelength forms a standard for local area fiber-optic networks (the other standard wavelength is 1.3 .mu.m, where no manufactured VCSEL technology yet exists). In a flip-chip bonded VCSEL, the light must be emitted through the bottom surface, i.e., the substrate side of the VCSEL chip. For 850 nm operation then, the opaque GaAs substrate must be removed. The GaAs substrate is removed after the VCSEL chip is flip-chip bonded to a semiconductor chip (see, e.g., U.S. Pat. No. 5,385,632, issued on Jan. 31, 1995). Unfortunately, this means that the VCSEL chips cannot be tested until they have already been mounted. This destroys one of the major advantages of VCSELs over edge-emitting lasers, which is that VCSELs can be tested on the wafer before cutting the wafer into individual chips. Moreover, if the VCSEL is bad then the bonded VCSEL/semiconductor chip must be discarded. What is desired is a technique to test VCSEL devices while they are still part of the wafer.